An assembly of this kind is known from DE 103 59 851 A1, for example, which is incorporated by reference.
A particular physical effect leading to air being introduced into the hydraulic brake system and consequently to a reduced braking effect can occur in a “handbrake control” on motorcycles.
At high accelerations and excitation frequencies of above 300 Hz, the effect observed involves air bubbles being mixed into the brake fluid. The introduction of air bubbles from the air buffer above the surface of the liquid takes place in the pressure medium reservoir. At the critical accelerations and frequencies mentioned, there is then the special physical effect that these air bubbles fall to the bottom of the pressure medium reservoir, counter to their buoyancy force, and remain there while the ambient conditions concerned persist.
In the case of the known assemblies, some of the air bubbles can enter the master cylinder via the pressure medium connection. If there is then a brake actuation, some of the air is carried into the pressure chamber of the master cylinder during the brake release operation owing to the folding over of a master cylinder cup seal and leads there to an increased lever travel or a reduced braking effect during subsequent braking operations.